The present invention relates to a stator of a motor such as a brushless motor of inner rotor type.
FIG. 6 is a sectional view of a part of a so-called inner rotor type brushless motor in which a rotor is disposed inside a stator so as to rotate, and FIG. 7 is an enlarged sectional view taken along a line (vii)-(vii) in FIG. 6.
A rotor 21 includes a rotor shaft 22, a rotor core 23 fixed to the rotor shaft 22, and a rotor magnet 24 which is provided on an outer peripheral surface of the rotor core 23 or inside thereof.
A stator 25 includes a stator core 26 which is annularly continued, and coils 28 which are respectively wound around tooth parts 26b projecting from the stator core 26 inward in a radial direction, by way of insulators 27.
The stator core 26 is formed of laminated magnetic steel sheets and includes a stator core body 26a in an annular shape, a plurality of tooth parts 26b which are projected inward in the radial direction from the stator core body 26a, equidistantly along an inner circumferential direction thereof. Each of the tooth parts 26b generally includes protruded parts 26c which are protruded to opposite sides in the circumferential direction at a distal end side thereof (a side opposed to the rotor).
Each of the insulators 27 which is clamped by the stator core 26 from opposite sides in an axial direction of the stator is formed of resin or the like, and has a body part 27a which is engaged with an outer peripheral surface of the tooth part 26b of the stator core 26, and a flange part 27b which is formed in at least one end of the body part 27a. The two body parts 27a, 27a which are adjacent to each other in the circumferential direction are annularly connected by means of a connecting part 27c. 
Each of the coils 28 is fitted around the tooth part 26b of the stator core 26 by way of the aforesaid insulator 27. In assembling, the coil 28 is wound around the body part 27a of the insulator 27, after the body part 27a has been fitted to the tooth part 26b of the stator core 26 from opposite sides in the axial direction (Reference should be made to Patent Document 1). This method of winding is called as a concentrated winding method.
In the motor provided with the above described stator, an end surface of the distal end portion of the tooth part 26b including the protruded parts 26c functions as a magnetic pole surface of the stator, while an outer peripheral surface of the rotor magnet 24 functions as a magnetic pole face of the rotor.
By the way, in the above described stator 25, the end surface of the tooth part 26b which functions as the magnetic pole face of the stator spreads to opposite sides in the circumferential direction because of presence of the protruded parts 26c, but does not spread to opposite sides in the axial direction. As shown in FIG. 7, there is only the flange part 27b of the insulator 27 at opposite sides of the end surface of the tooth part 26b in the axial direction. For this reason, a part of a magnetic flux Mo from the rotor magnet 24 leaks through the flange part 27b, at opposite sides of the magnetic pole face of the stator in the axial direction. As the results, in the conventional stator 25 of this type, an entrapping rate of the magnetic flux from the rotor magnet 24 has been low, and this is considered to be one of causes for deterioration of rotation performance of the motor.
Moreover, spaces at opposite sides of the magnetic pole face of the stator in the axial direction have not been effectively utilized for the purpose of confining the magnetic flux, entrapping the magnetic flux, and preventing leakage, although the spaces are at coil ends, and these spaces have been magnetically useless spaces, in the prior art.
Patent Document 1: JP-A-2000-60046